The accuracy of blood glucose monitoring: no need for alarm

We recently read an article in the New York Times about the accuracy of blood glucose monitors and whether the official accuracy standards for the devices need to be changed. This is an important issue, to be sure — millions of people with diabetes manage their diabetes treatment and dose their insulin based on the numbers from glucose monitors — but it’s also important not to let one article shake your faith in one of the most important tools we have in the struggle with diabetes.

The Times did a good job of presenting a “worst-case” scenario about the accuracy of meters, but in our view, the article overstated the problems and didn’t take into account how important meters are for good control.

Let’s talk about the numbers. Current standards from the International Organization for Standardization (IOS) require that nearly all (95%) of results from a glucose monitor have to be within 20% of the actual glucose value — as the Times reported. Later in the article, however, it cited a study of five common glucose monitors, saying that “results varied by as much as 32 percent.” What was not stated clearly in the article was that these five meters were never compared to the actual glucose value, only to each other — and that the 32% number was from the worst comparison between two meters (out of 10 possible combinations), and ONLY when the meters were used with old strips, and ONLY in the 70-100 mg/dL range. In contrast, the average variability between meters (with old or fresh strips, and across all glucose ranges) was about 9%, and the variability using only fresh strips was about 6%.

So what’s wrong with the Times article? While the accuracy of blood glucose meters is clearly a serious concern, it’s important to take the time to fully understand the data and to anticipate the reaction of people with diabetes upon learning that their meter is (potentially) off by 32%. We were alarmed that the results of Morgan DiSanto-Ranney’s high school science project could lead to her father testing less — as inaccurate as meters are, people with diabetes are certainly better off with them than without them. How can you figure out where to go with blood glucose if you don’t even know where you start? A recent literature review in JAMA evaluated large, recent trials showing that testing with a glucose monitor helps to improve control, which in turn reduces the complications of diabetes.

In addition, the Times missed out on the chance to give people with diabetes some really valuable information: for example, that meters are more precise when used with fresh test strips, that it’s very important to make sure patients test when their hands are clean (logical information that you would think would be unnecessary to convey, but studies have also shown problems on this front in “real life”), and that all meters are not created equal (one of the meters, dubbed meter “E”, seemed to perform worse than the others, and was one of the two meters in the comparison producing the 32% difference).

People with diabetes (and people in general) don’t have the time to follow up on every statistic in an article. We count on the media to represent issues fairly and consider the context of each article’s argument. In this regard, we believe the recent Times article on the accuracy of blood glucose monitoring fell short of the mark. Blood glucose monitoring is an important tool in diabetes management, and it will continue to be useful regardless of whether or not accuracy standards are changed.